My introduction to the Roman army was in Amgueddfa Lleng Rufeinig Cymru, the National Roman Legion Museum of Wales in Caerleon. It is such a vast subject, maybe a good way in is through such a museum.

• Amgueddfa Lleng Rufeinig Cymru, The National Roman Legion Museum of Wales

Knight, J. K. Caerleon Roman Fortress. 3rd edn. Cardiff: Cadw: Welsh Historic Monuments, 2003.

I have found two introductions of great help.

Pollard, Nigel, and Joanne Berry. The Complete Roman Legions. London: Thames & Hudson, 2012.

Goldsworthy, Adrian. The Complete Roman Army. London: Thames & Hudson, 2015.

The focus on Roman army studies has shifted towards the people who served in the army, and their livelihoods. Ian Haynes has been a key proponent in that changed emphasis.

Haynes, Ian. Blood of the Provinces: The Roman Auxilia and the Making of Provincial Society from Augustus to the Severans. Illustrated edition. Oxford: Oxford University Press, 2013.

Haynes, Ian. ‘Identity and the Military Community in Roman Britain’. In The Oxford Handbook of Roman Britain, edited by Martin Millett, Louise Revell, and Alison Moore, 448–77. Oxford: Oxford University Press, 2016.

This approach was the inspiration behind the recent British Museum exhibition, Legion: Life in the Roman Army. Thought the exhibition is long since finished, the book published to go with the exhibition is an excellent study of life in the Roman Army. Among many others, three things in particular caught my eye, a virtually complete leather tent (pages 182-83), the Cambridgeshire Crucfixion (pages 271–74), and the depiction of Cavalry sports helmets representing heroes from Troy (pages 138-39)

Abdy, Richard Anthony. Legion: Life in the Roman Army. London: The British Museum, 2024.

A more popular approach to life in the army is offered by Guy de la Bédoyère.

Bédoyère, Guy de la. Gladius: Living, Fighting and Dying in the Roman Army. London: Abacus, 2021.

Christopher Zeichmann has made a specific study of the Roman Army in Palestine. His work has also proved invaluable. In particular his database of military inscriptions and papyri of early Roman Palestine is a treasure trove of information.

Zeichmann, Christopher B. The Roman Army and the New Testament. Lanham, Maryland: Fortress Academic, 2018.

• Zeichmann, Christopher B. Essential Essays for the Study of the Military in First-Century Palestine: Soldiers and the New Testament Context. 1 online resource (138 pages). La Vergne: Wipf and Stock Publishers, 2019.
• Zeichmann, Christopher B. ‘Military Forces in Judaea 6–130 CE: The Status Quaestionis and Relevance for New Testament Studies’. Currents in Biblical Research 17, no. 1 (2018) 86–120. 
• Zeichmann, Christopher B. ‘Database of Military Inscriptions and Papyri of Early Roman Palestine’. Database of Military Inscriptions and Papyri of Early Roman Palestine. At, 2018.